A semiconductor substrate made of silicon is used as a photoelectric conversion material in a general crystalline solar cell element. The semiconductor substrate includes a passivation layer on a surface thereof. The passivation layer is formed of aluminum oxide, for example. Properties of aluminum oxide easily change due to a penetration of moisture. Thus, performed is a formation of a protective layer of oxide or nitride by a plasma enhanced chemical vapor deposition (PECVD), for example, on the passivation layer.